The invention relates to vapor flow indicators for fuel dispensing systems.
Systems for dispensing fuel into vehicles, e.g. at gasoline stations, typically employ a coaxial hose, which, in so-called inverted arrangement, has an outer conduit for delivery of fuel to the vehicle and an inner conduit for recovery of fuel vapors displaced from the vehicle tank. Recent field testing by the California Air Resources Board (CARB) of vacuum assist vapor recovery systems for use in fuel dispensing systems uncovered a problem with the inverted coaxial hose. They found that the internal vapor hose can kink during normal operation, causing substantial blockage of the vapor return pathway. Once kinked, these hoses tend to remain in a tube-collapsed condition, thus permanently reducing the cross sectional area of the vapor flow path.
Vacuum assist systems which employ a variable speed vane pump, or other flow control device mounted in the dispenser, use the electronic pulses related to the liquid gasoline flow rate to control the vane pump speed or the orifice size of a variable orifice restrictor. Using this technique, the volumetric rate of vapor recovery is maintained in proportion to the rate of liquid gasoline delivery.
A kink in the vapor hose will act to restrict vapor flow, thus changing the absolute pressure on the inlet side of the vapor flow control device. The reduction in pressure results in a reduction in throughput for both the vane pump and the variable orifice flow control device. A kink in the vapor hose can therefore result in escape of gasoline vapor in the vehicle tank fillpipe to the extent that the vapor recovery throughput is reduced at the flow control device.
In practice, the detection of a damaged vapor hose in the service station is not easy, since the outer hose might not show any physical sign of kinking. This type of defect can only be found through extensive testing or by a process of elimination of other vapor recovery related components.
According to one aspect of the invention, a vacuum assist vapor recovery system, e.g. in or for a fuel dispensing system, having a coaxial hose with an outer fuel conduit for delivery of fuel and an inner vapor conduit for recovery of vapor comprises an indicator assembly for providing indication of vapor flow reduction in the inner vapor conduit, e.g., due to restriction of flow cross-section in the inner vapor conduit or failure of a vacuum pump or other vacuum control device, the indicator assembly comprising a detector element in communication with the inner vapor conduit for detection of vapor flow within the inner vapor conduit and an indicator element of vapor flow for indication of vapor flow within the inner vapor conduit detected by the detector element.
Preferred embodiments of the invention may include one or more of the following additional features. The indicator assembly further comprises a housing defining a chamber in communication with the inner vapor conduit, a paddle mounted to pivot in the chamber between a first position indicating relatively low or no flow and a second position indicating relatively higher flow, spring means biasing the paddle toward the first position, and a window for viewing into the chamber from external of the housing, the paddle having a first end portion disposed in a flow of vapor through the inner vapor conduit, the first end portion being moved from the first position toward the second position by vapor flow in the inner vapor conduit for detection of vapor flow within the inner vapor conduit, and the paddle having a second end portion disposed in view of the window, the second end portion being moved from the first position toward the second position in response to movement of the first end portion in detection of flow of vapor for indication of vapor flow within the inner vapor conduit. The indicator assembly further comprises a housing defining a chamber in communication with the inner vapor conduit, a paddle wheel comprising a body with a plurality of paddles extending therefrom generally radially in a plane of rotation, the paddle wheel being mounted to rotate in the chamber in response to flow of vapor in the inner vapor conduit, and a window for viewing into the chamber from external of the housing, at any time, one or more of the plurality of paddles being disposed in a flow of vapor through the inner vapor conduit, the one or more paddles being moved and the paddle wheel being rotated by vapor flow in the inner vapor conduit for detection of vapor flow within the inner vapor conduit, and one or more other of the plurality of paddles being disposed in view of the window, the one or more other of the plurality of paddles being moved relative to the window in response to movement of the one or more paddles of the plurality of paddles in detection of flow of vapor for indication of vapor flow within the inner vapor conduit. The indicator assembly further comprises a module, the module being reversible 180xc2x0 relative to the housing to permit alternative placement of the housing, including where vapor flows in an opposite direction. The detector element comprises a Venturi device disposed in communication with the inner vapor conduit, the indicator assembly comprises a differential pressure gauge, and the indicator element comprises an electronic display of flow rate. The detector element comprises a Venturi device disposed in communication with the inner vapor conduit, the indicator assembly comprises a differential pressure transducer, and the indicator element comprises an electronic display of flow rate. The detector element comprises a paddle wheel comprising a body with a plurality of paddles extending therefrom generally radially in a plane of rotation with signal elements mounted to one or more of the paddles of the paddle wheel, and the indicator element comprises a proximity sensor responsive to the signal elements mounted upon the paddle wheel and an electronic display of flow rate. The indicator assembly further comprises a housing defining a chamber in communication with the inner vapor conduit and adapted for mounting vertically, and a float ball rotameter comprising a precision float ball disposed for movement between a lower pin and a spaced apart upper pin, the upper and lower pins defining a chamber therebetween, the precision float ball adapted move in the chamber between a first position in proximity to the lower pin indicating relatively low or no flow and a second position in proximity to the upper pin indicating relatively higher flow, and a window for viewing into the chamber from external of the housing, the precision float ball being lifted from the first position toward the second position by vapor flow in the inner vapor conduit for detection of vapor flow within the inner vapor conduit, and movement of the precision float ball between first position and the second position in response to flow of vapor providing indication of vapor flow within the inner vapor conduit. The detector element comprises a Venturi device disposed in communication with the inner vapor conduit and a diaphragm responsive to a differential of pressure between the Venturi device and the inner vapor passageway, and the indicator element comprises a pointer associated with a scale and moveable relative to the scale in response to movement of the diaphragm. The detector element comprises a Venturi device disposed in communication with the inner vapor conduit and a differential vapor transducer responsive to a differential of pressure between the Venturi device and the inner vapor passageway, and the indicator element comprises a signal indicative of the vapor flow rate from the differential pressure transducer.
Preferred embodiments of a fuel dispensing system of the invention may also include one or more of the following additional features. The fuel dispensing system further comprises a comparator adapted to receive the signal indicative of vapor flow rate and a corresponding signal indicative of liquid flow rate. Preferably, the comparator is further adapted to issue a signal when vapor-to-liquid flow rate outside a predetermined range is detected. More preferably, fuel dispensing system further comprises a signal receiver adapted to receive the signal issued by the comparator and discontinue flow of liquid fuel.
According to another aspect of the invention, a method for monitoring vapor-to-liquid flow rate in a fuel dispensing system with a vacuum assisted vapor recovery system having a coaxial hose with an outer fuel conduit for delivery of fuel and an inner vapor conduit for recovery of vapor comprises the steps of: determining vapor flow rate in the inner vapor conduit; issuing a signal indicative of the vapor flow rate; determining liquid fuel flow rate in the outer fuel conduit; issuing a signal indicative of the liquid fuel flow rate; comparing the signal indicative of the vapor flow rate and the signal indicative of the liquid fuel flow rate; and, when vapor-to-liquid flow rate is outside a predetermined range, issuing a signal to discontinue flow of liquid fuel.
An object of the invention is to provide a device for indication of vapor flow within the inner conduit of a coaxial fuel dispensing hose in order to detect restriction of the vapor flow path, e.g., due to kinking of the inner hose or faulty performance of the vapor flow control device or pump.
Other features and advantages of the invention will be apparent from the following description of a presently preferred embodiment, and from the claims.